Ceramic modules including electronic components, such as ICs, SAW filters, resistors, capacitors, and coils, mounted on a ceramic substrate having a wiring pattern thereon is disclosed in Japanese Patent Laid-Open Publication Nos. 3-205857 and 4-252041.
FIG. 18 is a cross sectional view of a conventional ceramic module 50. The ceramic module 50 includes a component 60, such as a capacitor and an inductor, an active component 80, such as an IC and a SAW filter, and a ceramic substrate 70. The ceramic substrate 70 includes internal electrodes 51, via electrodes 52 connecting between the internal electrodes 51, land electrodes 55 connected with the active component 80 and the component 60 for surface-mounting them, and back electrodes 56 for mounting the ceramic module 50 on a mother board. The end electrodes 62 of the component 60 are connected to land electrodes 55 corresponding to them with a conductive adhesive 61, such as solder, while the back electrodes 81 of the active component 80 are connected to land electrodes 55 corresponding to them with a conductive adhesive 61. A gap between the active component 80 and the substrate 70 is filled with a resin 90 for increasing reliability of surface mounting of the active component 80.
In the conventional module 50, the component 60 and the active component 80 are mounted on the ceramic substrate 70 which has been baked, and may be molded with a resin 91 according to requirement.
When the component 60 has a small size, such as 1005 size or 0603 size, the conventional module 50 includes a small amount of the conductive adhesive 61 for avoiding short-circuit between the electrodes during the surface mounting. When being applied for molding the component 60 mounted, the resin 91 may fail to flow into beneath the component 60, and may produce a gap 92. When the ceramic module 50 is mounted on the mother board, the conductive adhesive 61, such as solder, may melt and flow into the gap 92 between the component 60 and the ceramic substrate 70, hence causing a short-circuit between the land electrodes 55 and disturbing the performance and the operational reliability of the ceramic module 50.
The resin 90 is also applied to between the component 80 and the substrate 70 for mounting and securing the component 80 onto the substrate 70. The resin 90, upon not being applied sufficiently between the component 80 and the substrate 70, may reduce the bonding strength and the operational reliability.